The field of the invention is earthquake actuated gas shutoff valves. There is a large variety of designs of such valves. One such valve is shown in U.S. Pat. No. 5,823,223 which has a ball held on a pedestal. This patent is a continuation in part of U.S. Pat. No. 5,603,345. During an earthquake the ball of the '223 patent falls off of the pedestal and falls over a valve seat. The valve is reset externally by turning an arm which moves the ball off of the valve seat and back onto the pedestal. Another design is shown in U.S. Pat. No. 5,704,385 where a ferromagnetic ball rolls out of a depression and causes a valve member to move against a valve seat thereby blocking the flow of gas. In a different embodiment, the ball is held in a depression and rolls into a valve seat in the gas flow path. The ball is manipulated magnetically to reset the valve.
Another version of a ball which rolls out of a higher position to a lower position where it blocks a valve seat is shown in U.S. Pat. No. 5,603,345. Yet another version of a ball held in a depression which moves into a valve seat is shown in U.S. Pat. No. 5,052,429. Another version is shown in U.S. Pat. No. 4,889,150. Still another valve using a ball resting on a pedestal is shown in U.S. Pat. No. 4,715,394. A relatively simple design is shown in U.S. Pat. No. 3,747,616 where the ball is reset by a string attached to the ball.
One inherent disadvantage of using a steel ball is the damage the steel ball can do during shipping. Various approaches have been used to reduce this problem, some of which involve the addition of packing materials during shipping. Occasionally, during installation, the installer will forget to remove the packing materials. Also, many of the prior art valves do not have any means of determining when the valve is open or closed from the exterior of the valve.